IN THIS SECTION
Explore our collection of Hudson River lesson plans, videos and online activities to support hand on investigations of the Hudson River in your classroom. Topics include watersheds, tides, estuaries, and aquatic life found in the Hudson River.
K-12 Curriculum Guide
These inquiry-based, multi-component STEM education units are a guide for teachers and students to deepen their understandings of the Hudson River and its watershed. These interdisciplinary units are designed to engage diverse learning styles, introduce students to the big ideas in science, build their knowledge of environmental issues and help them connect to the natural world around them. The lessons have been reviewed by classroom teachers, and other curriculum specialists.
Water & Watersheds
- Estuary Unit Grade 2-3 (PDF)
- Estuary Unit Grade 4-5 (PDF)
- Estuary Unit Middle School (PDF)
- Estuary Unit High School( PDF)
Climate & Weather
Interdependence in Ecosystems
Human Impacts, Benefits & Solutions
A Day in the Life of the Hudson and Harbor
- DITL Elementary (PDF)
Lessons by Grade Level
K-3 Grade Lessons
This collection is designed to allow teachers of young children to engage in standards-based study of the Hudson River.
- Package including teacher’s section and all K-3 lessons (PDF)
- Meet the Hudson River/Mapping the Hudson River (PDF)
- Growing Up as a Dragonfly (PDF)
- Growing Up as an American Eel (PDF)
- Growing Up as a Striped Bass/How Big? How Old? (PDF)
- Hogchoker Hunt/Camouflage Hunt (PDF)
- What Do Animals Need To Stay Alive? HABITAT! (PDF)
- What Do Animals Need To Stay Alive? FOOD! (PDF)
4-7 Grade Lessons - English language Arts
These lessons allow teachers to integrate study of the Hudson into instruction in English Language Arts.
Readings in Hudson River Natural History
- From the Mountains to the Sea (PDF)
- The Atlantic Sturgeon of the Hudson River (PDF)
- Bald Eagles of the Hudson River (PDF)
- The Eel’s Incredible Journey (PDF)
- Blue Claw! (PDF)
- Adaptations – Designs for Survival (PDF)
- Adapting to Estuaries (PDF)
- Alien Invasion! (PDF)
- Teacher Package for “Readings in Hudson River Natural History” (PDF)
Water Cycle Reading and Writing
Students will read a story about a water molecule’s journey through the water cycle and then write a similar story.
4-7 Grade Lessons - Mathematics
These lessons use Hudson River data to interpret information that require mathematic skills for their solution.
- Mathematics Lesson Package (PDF)
- Hudson River Miles Map (PDF) Note: The map is designed for legal (8.5 inches x 14 inches) paper to maximize legibility, but it will work on letter (8.5 inches x 11 inches) paper as well.
4-7 Grade Lessons - Science
These lessons explore physical and life science topics related to the Hudson. They make use of data collected by scientists, students, and others studying the river.
Hudson River Miles Map (PDF) Note: The map is designed for legal (8.5 inches x 14 inches) paper to maximize legibility, but it will work on letter (8.5 inches x 11 inches) paper as
Dining Out With Fishes and Birds of the Hudson
- Student section for “Dining Out With Fishes and Birds of the Hudson” (PDF)
- Teacher section and answer key for “Dining Out With Fishes and Birds of the Hudson” (PDF)
Fish Communities in the Hudson
- Student section for “Fish Communities in the Hudson” (PDF)
- Teacher section and answer key for “Fish Communities in the Hudson” (PDF)
Which Fish Where?
- Student section for “Which Fish Where?” (PDF)
- Teacher section and answer key for “Which Fish Where?” (PDF)
Finding the Salt Front
- Student section for “Finding the Salt Front” (PDF)
- Teacher section and answer key for “Finding the Salt Front” (PDF)
The Hudson’s Ups and Downs
- Student section for “The Hudson’s Ups and Downs” (PDF)
- Teacher section and answer key for “The Hudson’s Ups and Downs” (PDF)
Mapping Where Animals Live
- Student section for “Mapping Where Animals Live” (PDF)
- Teacher section and answer key for “Mapping Where Animals Live” (PDF)
These Maps Are For The Birds
- Student section for “These Maps Are For The Birds” (PDF)
- Teacher section and answer key for “These Maps Are For The Birds” (PDF)
Science Lesson Package
4-7 Grade Lessons - Key Understandings about the Estuary
- The lower Hudson is an estuary in which salty seawater pushes upriver, diluted by fresh water as it moves inland. The leading edge of dilute seawater generally ranges between the Tappan Zee and Newburgh, depending on the volume of freshwater runoff from the watershed. The plants and animals found at any place in the estuary reflect the prevailing salinity at that site.
- Ocean tides influence the Hudson north to Troy, NY. The estuary typically experiences two high tides and two low tides each day. Organisms living in its shallows are adapted to survive and prosper while alternating between exposure to the air and submergence in water.
- In the Hudson, as in most ecosystems, solar energy captured by green plants is made available to food webs. However, much of the energy that fuels this ecosystem does not come from plants living in the estuary. Instead, it comes from the watershed as detritus – decaying organic matter such as tree leaves – that enters food webs via bacteria and invertebrates that eat detritus.
- Erosion, deposition, and other forces create habitats that support distinct communities of diverse plants and animals along the Hudson. Life in these habitats varies according to a mix of physical and chemical factors including depth, tides, salinity, and exposure to waves and ice.
- The Hudson estuary is an important component of larger regional ecosystems such the coastal Atlantic Ocean. It provides critical spawning habitat for valuable coastal fish including striped bass, wintering habitat for eagles from northern Canada, and rest stops for migratory species that travel through the system and beyond.
- The Hudson was a linchpin in Revolutionary War strategies, and as a result was memorialized as our first national river.
- The Hudson’s sea level course through the Highlands was key to realizing the dream of the Erie Canal, which made New York the Empire State and vaulted New York City to its leading role as a center of finance and trade. The river remains an important route for commerce today.
- Early in our history, Americans forged a national identity that valued the wild landscape of the Hudson Valley. The aesthetic appeal of wild nature, celebrated by painters and writers, led to the preservation movement and, in the crucible of the Storm King battle, the modern environmental movement.
- Once badly polluted with human sewage and industrial wastes, the Hudson is healthier now, thanks mainly to the Clean Water Act, which required sewage treatment and regulated other waste discharges. Remaining issues include non-point source pollution from the watershed and a legacy of toxic pollutants in sediments. The scale of physical alteration of the estuary by humans makes restoration of an idealized, pre-industrial ecosystem virtually impossible.
- Estuary management programs encourage input from many stakeholders to formulate policies guiding development in a context of environmental protection. Disputes over environmental impacts do arise and are resolved through the political process and a framework of legislation interpreted and enforced by regulatory agencies and the courts. Citizens play crucial roles as participants in this process and as stewards of the river.
Supported by NYSDEC and Cornell University, the Virtual River Program offers dozens of videos, lesson plans, and opportunities to connect directly with education staff.
Explore units of Hudson River study organized by topic with short video updates, complementary lesson plans, and other online interactives. Lessons are updated frequently with the newest topics at the top. Enjoy exploration of the Hudson River Estuary and Watershed with our enthusiastic team!
Turbidity and Salinity
- Turbidity and Salinity of the Hudson River (short video from NYSDEC)
- Estuary Water Demonstration (short video demonstration from NYSDEC)
- Tracking the Salt Front (lesson plan for Elementary Students) and Teacher Guide
- Finding the Salt Front (lesson plan for Middle School Students) and Teacher Guide
- Salinity Data Visualization (lesson plan for High School Students) with (Student 2008 Data &
Student 2009 Data)
We recommend you begin by watching this week’s short Turbidity and Salinity video from our educators at NYSDEC. Then, check out our Estuary Water Demonstration. Elementary students should complete the Tracking the Salt Front lesson plan which is accompanied by a Teacher Guide. Middle school students will enjoy the Finding the Salt Front lesson plan, also accompanied by a Teacher Guide. High School students are directed to the Salinity Mapping and Data Visualization Activity with data sets and maps from two different years (2008 and 2009).
Fish and Climate Change
- Hudson Fish and Climate Change (short video from NYSDEC)
- Climate Change and the Hudson River (High School student lesson plan from Cary Institute) and Answer Key (for teachers)
- Which Fish are Where? (Middle School student lesson plan from NYSDEC) and Answer Key (for teachers)
- Bird, Butterfly, Eel (Elementary student story-time from NYSDEC)
We recommend everyone watch the short Hudson Fish and Climate Change video from our educators at NYSDEC. Then, we suggest choosing the lesson plan that fits your grade range with Climate Change and the Hudson River (High School), Which Fish are Where? (Middle School), and Bird, Butterfly, Eel (Elementary School) for age appropriate options.
Sea Level Rise on the Hudson River
- Global Sea Level (short video from NASA)
- Measuring Sea Level Rise (short video from NYSDEC)
- Climate Change and Sea Level Rise Unit (lesson plans from Cary Institute of Ecosystem Studies)
- Investigating Climate Change (Elementary School activities in Conservationist Kids)
We recommend watching the short Global Sea Level Rise video from NASA for a general introduction to this topic. Then, we suggest watching the Measuring Sea Level Rise video for some Hudson River context from our education team. For Middle and High School students, we highly encourage digging into the Climate Change and Sea Level Rise lesson plans with data analysis, map investigations, and action plan assessments for the Hudson River Estuary. For Elementary School students, we think Investigating Climate Change in Conservationist Kids is a wonderful set of readings and resources to explore.
Microplastics and Marine Debris
- Microplastics and Marine Debris (NYSDEC Short Video)
- Hudson River Microplastics (NYSDEC Power Power Presentation)
We suggest you begin your exploration of this topic with our introductory Microplastics and Marine Debris short video followed by looking at power point presentation called Hudson River Microplastics.
Day in the Life of the Hudson River
Day in the Life of the Hudson River an incredible community education science event on the banks of the estuary. These videos portray river science through the eyes of the students, who can follow along with data collection sheets at home, and take a deeper dive with a guest scientist at the end of each video. The videos are divided by geography, from New York Harbor to the Troy Dam, and beyond.
- Upper Estuary (Poughkeepsie to Troy and beyond): Video/Data Sheet
- Lower Estuary (Yonkers to Beacon/Newburgh): Video/Data Sheet
- NY Harbor (and connected waterways): Video/Data Sheet
We recommend watching the video from your region of the Hudson River first. Then, download the accompanying data sheet to fill out while you re-watch that video. We encourage you to move onto the other two videos and data sheets. This will give you a wonderful overview of the entire Hudson River Estuary and data collected at many different locations.
Hudson River Fish: Identification and Adaptations
- Clearwater Fish Key (online interactive fish identification tool)
- Identify Live Hudson River Fish (short video update from DEC Educators)
- Sturgeon Reading (short reading) and Sturgeon Adaptations in Hudson River (short video from NYSDEC Fisheries about Sturgeon)
- Fish Diagram (visual aid), Body Part Shapes of Fish (visual aid), and Fish Form and Function (lesson plan for individual work using visual aids)
- Clearwater Fish Quiz (short online fish quiz)
We suggest starting this week’s update by opening the “Clearwater’s Fish Key” in one window first. Then, we recommend watching the “Identify a live Hudson River Fish” video, and be ready to pause the video for identifying the fish on your own. We then recommend individually completing the short “Sturgeon Reading” before watching the “Sturgeon Adaptations in the Hudson River” video about another amazing fish found in the Hudson. We suggest using the next three resources together. Then, we suggest going through the fun “Identify a Fish Game” followed by testing your new knowledge with the “Clearwater Fish Quiz.”
High Tides and Low Tides
- Tide Finder (Short video about Hudson River Tides from DEC Educators)
- Tides (Short animated video from ORCA)
- Tides in the Hudson River (Short reading assignment from Cary Institute) and Tides Questions (student questions to accompany reading)
- Tides and Currents (Detailed reading from Cary Institute)
- Tidal Cycle on the Hudson River Estuary (Visual aid from Cary Institute)
- Hudson Ups and Downs (student lesson plan from the DEC) and Ups and Downs (teacher version with answer key)
We recommend beginning your exciting exploration of the Tides with “Tide Finder” for a wonderful short video by our DEC educators. Then, we encourage you to watch the animated “Tides“ video. Then we encourage students to read “Tides in the Hudson River” and answer the “Tides Questions.” If students are looking for a more detailed description and graphical representation of how water moves in the estuary, we challenge them to explore “Tides and Currents.” After reading and reflecting on these processes, we recommend examining the “The Tidal Cycle on the Hudson River Estuary” visual aid. For a deep dive into the topic, we suggest students complete “Hudson Ups and Downs” as an assessment tool while teachers make use of the answer key.
- What is a Watershed? (short video about watersheds from DEC Educators)
- Watersheds! (animated video from the NOAA and NSF)
- Hudson River Watershed Map (detailed color map)
- Introduction to the Hudson River Watershed (powerpoint presentation from the Cary Institute of Ecosystem Studies)
- What’s a Watershed? (reading) and Watershed Questions (reflection questions from the Cary Institute of Ecosystem Studies)
- Model My Watershed (interactive webpage) and How to Model My Watershed (Student Lesson Plan and Teacher Key)
- Water Cycle (interactive webpage)
We recommend beginning your exciting exploration of the Hudson River Watershed with our “What is a Watershed?” short video from our DEC educators. Then, we encourage you to enjoy the entertaining “Watersheds!” animated video. After watching these we recommend opening the “Hudson River Watershed Map” to examine what our local watershed looks like. Then, we suggest going through the “Introduction to the Hudson River Watershed” powerpoint presentation. Next, dig into the “What’s a Watershed?” reading and complete the “Watershed Questions.” For more advanced students, we encourage you to open the interactive online lesson, “Model My Watershed” webpage while turning up your volume and listening to the “How to Model My Watershed” narrated presentation and directed activity. For younger students, we suggest checking out the “Water Cycle” webpage.
What is an Estuary?
- What is an Estuary? (short video update from DEC Educators)
- What is an Estuary? (short video from NOAA about National Estuarine Research Reserves around the nation)
- Estuaries: Nature’s Water Filters (online interactive presentation and game from NOAA)
- From the Mountains to the Sea (lesson plan for individual work at home)
- Test your Estuarine Knowledge (short online quiz)
We suggest beginning by watching the two short videos called “What is an Estuary?” by our DEC educators and by NOAA. We then suggest going through the “Estuaries: Nature’s Water Filters” online interactive presentation and game. From there you can do the individualized lesson plan called “From the Mountains to the Sea.” Then, after having watched the videos, completed the interactive presentation, and finishing at least one of the lesson plans, we suggest every student complete the “Test your Estuarine Knowledge” online short quiz.
Hudson River Source to Sea
- Hudson River Source to Sea (short video about the path of the river from DEC Educators)
- From the River to the Sea (short reading with reflection questions from DEC)
- River Runs Through It (mapping lesson plan from the DEC) and Teacher’s Version (with answer key)
- How Much Water is in That River? (math lesson calculating river volume from Cary Institute)
- River (video of DEC educator reading children’s book by Elisha Cooper)
- Source To Sea (video about Riverkeeper’s citizen science monitoring project by Jon Bowermaster)
- Meet the Hudson River (short reading with assessment from DEC)
We recommend beginning your exciting exploration of the entire path of the Hudson River with the short “Hudson River Source to Sea” video by our DEC educators. “From the River to the Sea” is a simple reading with reflection questions that we suggest next. For younger students, we recommend completing the “River Runs Through It” lesson plan and watching the “River” story time video. And for older students, we suggest completing the “How Much Water is in That River?” lesson plan and viewing the beautiful “Source to Sea” video about Riverkeeper’s citizen science work. For an assessment of understanding for any age, we recommend reading and completing the mapping exercise called “Meet the Hudson River.”
- Geology of the Hudson Valley (short video update from DEC Educators)
- Geology of the Hudson Highlands (online reading and video from Garrison Union Free School)
- Sedimentary Rock Formation (reading and lesson plan)
- Common Fossils of New York (an identification key)
- Eurypterid Coloring Sheet (coloring page from NYS Museum)
We suggest you begin by watching the short video called “Geology of the Hudson Valley” by our DEC educator. Next, “Geology of the Hudson Highlands” is a wonderful resource with readings and a video for students. Then, we recommend looking at “Sedimentary Rock Formation” lesson plan and the “Common Fossils of New York” visual aid. Younger students, will enjoy the “Eurypterid Coloring Sheet.”
Birds and Birding
- Birding on the Hudson River Estuary (short video update from DEC Educators)
- Black Birders’ Week (Audobon Society website)
- Live Bird Webcams (Cornell Lab of Ornithology)
- Visual Identification (Cornell Lab of Ornithology guide to bird identification)
- The Falconer (Film with watch parties)
We suggest beginning by watching our short video called “Birding on the Hudson River Estuary” by our DEC educators. We then suggest checking out “Black Birders’ Week” website from the Audobon Society. From there you explore the two individualized Cornell Lab of Ornithology resources called “Live Bird Webcams” and the “Visual Identification” pages. Then we recommend looking at the film “The Falconer” which has watch parties this in celebration of Black Birders’ Week (May 30- June 5th).
Seining for Fish
- Seining for Fish (short video update from DEC Educators)
- Seining on the Hudson (short video NYSDEC from 2016)
- Hudson River Almanac Seining Excerpts (reading on seining in the Hudson)
- Conservationist for Kids Fishing! (publication for students about fishing in New York)
- Which Fish Where? (NYSDEC lesson plan for students) and Which Fish are Where? (teacher guide with answer key)
- Day in the Life of the Hudson River Data (lesson plan interpreting seining data from Lamont-Doherty Earth Observatory) and Day in the Life of the Hudson River Data (teacher guide with answer key)
- Create Almanac Observations (online form to submit observation of the natural world) and subscribe to The Almanac (weekly observations shared)
We recommend beginning your seining adventure with us by watching the “Seining for Fish” short video update from this spring. Then we suggested checking out the “Seining on the Hudson ” video of students seining for fish a few years ago. Then, we recommend older students read “Hudson River Almanac Seining” which is a short compilation of people’s experiences seining on the Hudson River. Younger readers will enjoy “Conservationist for Kids.” We’ve also provided two lesson plans with real data collected from seining the Hudson. The first lesson is “Which Fish Where?” with an accompanying teacher answer guide and the second lesson is “Day in the Life of the Hudson Data.” “ For a fun wrap up, we encourage students to make any observation about the natural world by looking out their window or visiting a safe outdoor space and submitting their observations to the “Create Your Almanac Observation” and subscribe to “The Almanac” to see observations in weekly newsletter.
- Hudson River Valley Turtles (short video update from DEC Educators)
- Woodland Pool Habitat and Swamp Habitat (two short reading about Hudson Valley turtle habitats)
- Mapping Where Animals Live (lesson plan for individual work at home) and Answer Key
- Turtle Shells (lesson plan for individual work at home)
- Terrapin Nesting Project (short video from the Turtle Conservancy about saving turtles)
- Create Your Own Turtle (short activity to demonstrate turtle knowledge)
We suggest beginning by watching the our short videos called “Hudson River Valley Turtles” by our DEC educators. We then suggest reading through the “Woodland Pool Habitat” and “Swamp Habitat” online readings to learn more about what kinds of habitats Hudson Valley turtles like. From there you can do the two individualized lesson plans called “Mapping Where Animals Live” and the “Turtle Shells” lesson plan. To see how people are helping protect turtles in our region, watch the short video “Terrapin Nesting Project.” Now we recommend synthesizing all your newly gained knowledge about turtles with the “Create Your Own Turtle” activity.
- Identification Sheet (simple identification sheet)
- Aquatic Macroinvertebrates (short video update from DEC Educators)
- Aquatic Benthic Macroinvertebrate Presentation (power point presentation on macroinvertebrate collection and identification)
- Macroinvertebrate Reading (short reading from the Cary Institute of Ecosystem Studies)
- Macroinvertebrate Questions (reflection questions from the Cary Institute of Ecosystem Studies)
- Bridging the Watershed Game (online game from the Ferguson Foundation)
- Atlas of Macroinvertebrates (interactive visual aid for identification)
We recommend beginning your exploration of aquatic macroinvertebrates with us by opening the “Identification Sheet” for quick reference of species you will become familiar with while watching the “Aquatic Macroinvertebrates” short video from our education staff. Then, we suggested checking out the self-directed “Aquatic Benthic Macroinvertebrate” powerpoint presentation. The “Macroinvertebrate Reading” followed by the “Macroinvertebrate Questions” are a good reading and reflection lesson that students can do at home to deepen their understanding and demonstrate their knowledge about these animals. Then we recommend playing the “Bridging the Watershed Game” for a fun way to test your new knowledge. For an amazing deeper dive into the secret lives of macroinvertebrates, explore the “Atlas of Macroinvertebrates.”
American Eels (Older Audience)
- Life Cycle Poster (illustration of Eel life cycle from DEC)
- The American Eel (short video update from DEC)
- Mapping the Migration of American Eels (lesson plan from DEC) and North Atlantic Map (for use with DEC lesson plan)
- The Hudson River Eel Project (video about citizen science project with students)
- Silky Love (Radiolab podcast about American Eel reproduction and life history)
For older students, we recommend beginning your exciting exploration of the American Eel by examining the “Life Cycle Poster” which beautifully illustrates how this animal grows. “The American Eel” video is a great next step on your journey with our education staff as we follow the migration path of this fish. After reviewing these resources, we suggest completing the “Mapping the Migration of American Eels” lesson plan from the DEC by using the accompanying “North Atlantic Map.” To learn about how students are involved with monitoring and conserving American Eels, check out the short video on “The Hudson River Eel Project.” Then, kick back and enjoy listening to an entertaining episode of Radiolab called “Silky Love” all about our favorite fish.
Vernal Pools and Salamanders
- Weird World of Vernal Pools (short video update from DEC Educators)
- Spotted Salamander Life Cycle (Life Cycle Poster and Podcast)
- Conservationist Kids Amphibian and Reptile Issue (DEC Magazine)
- Amphibian Migration Project (short video about NYSDEC citizen science) and Woodland Pool Conservation (NYSDEC webpage)
- Learn your Salamanders (identification sheet) and Salamander Identification Quiz (online game)
We recommend beginning your exploration of vernal pools by watching the “Weird World of Vernal Pools.” Then we suggested checking out the beautiful “Spotted Salamander Life Cycle” poster while you listen to the accompanying podcast about this species’ unique relationship with algae. We’ve also provided an elementary reading option with “Conservationist Kids – Amphibian and Reptile Issue.” Next, are two resources about how to get involved with a citizen science project helping amphibians to cross roads during their migration to vernal pools. The “Amphibian Migration Project” video can be viewed individually and the “Woodland Pool Conservation” webpage provides more information on how to protect these sensitive habitats. For a fun wrap up, look over the “Learn you Salamanders” identification sheet and take the “Salamander Identification Quiz.”
- Freshwater Tidal Marshes of the Hudson River (short NYSDEC education video)
- Habitats (Conservationist Kids)
- Build a Marsh (Lesson Plan from Cary Institute of Ecosystem Studies)
- Changes in Water Quality in Hudson River Wetlands (Data Jam from Cary Institute of Ecosystem Studies)
We encourage everyone to watch Freshwater Tidal Marshes of the Hudson River. Elementary students will enjoy reading Habitats. Middle and High School Students should delve into the Build-a-Marsh lesson plans. Advanced High School students will enjoy digging into real data in Changes in Water Quality in Hudson River Wetlands unit.
American Eels (Younger Audience)
- The Eel Story (Short storytime about eel life cycle from DEC Educators)
- Life Cycle Poster (illustration of Eel life cycle from DEC)
- The Incredible Eel (short reading with reflection questions from the DEC)
- Growing Up as an Eel (lesson plan from the DEC)
For younger students, we recommend beginning your exciting exploration of the American Eel with “The Eel Story” for a wonderful life cycle storytime. Then, we encourage you to examine the beautiful “Life Cycle Poster.” After enjoying those two resources we recommend moving onto “The Incredible Eel” reading with reflection questions and the “Growing Up as an Eel” lesson plan for individual student work at home.
Dissolved Oxygen and Temperature
- Dissolved Oxygen and Temperature of the Hudson River (short video from NYSDEC)
- Can the Ocean Run Out of Oxygen? (short video from Ted Talks)
- Day in the Life (short video from NYSDEC and Lamont-Doherty Earth Observatory) and Data Sheet
- Understanding Dissolved Oxygen (NOAA lesson plan and data) and Teacher Guide
We recommend you begin by watching this week’s short Dissolved Oxygen and Temperature video from our educators at NYSDEC. Elementary students should watch Can the Ocean Run Out of Oxygen? Middle and High School students can watch Day in the Life video to collect virtual water quality data on the accompanying Data Sheet. For an advanced data dive, students are directed to Understanding Dissolved Oxygen for interactive real-time dissolved oxygen analysis and the Teacher Guide is provided for a full unit on water quality data analysis for classroom use.